Arrangement for Producing Coatings on Substrates in Vacuo

ABSTRACT

The invention relates to an assembly for the formation of coatings on substrates in a vacuum, wherein a plasma is formed by means of electric arc discharge at least on one target connected as cathode, and the arc discharge will be ignited between an anode and the target by means of a deflectable focused laser beam which is directed through a window to the surface of the target. It is an object of the invention to provide a technical solution by means of which an undesired coating in the window area of a vacuum chamber can be distinctly reduced. According to the invention, for this a permanent magnet or electromagnet is disposed between the window and at least one target at the side next to, above or below the optical axis of the laser beam, and the laser beam is guided through a magnetic field developed by the permanent magnet or electromagnet.

The invention relates to an assembly for the formation of coatings onsubstrates in a vacuum, wherein a plasma is formed by means of electricarc discharge on at least one target connected as cathode, and the arcdischarge is ignited between an anode and the target by means of adeflectable focused laser beam being directed to the surface of thetarget. The laser beam emitted from a laser light source disposedoutside a vacuum chamber is then directed through a window being presenton the vacuum chamber into the vacuum chamber, and so to the surface ofthe respective target.

Thus, arc discharges can be ignited starting from the surface of atarget in different positions to be able to achieve uniform materialabrasion across a useful surface of a target. Thus, targets disposedinside of the vacuum chambers can be used over longer operating times,and at the same time a uniform coating formation can be achieved.

The deflection of such a laser beam can be achieved through conventionalsystems such as scanner systems or other suitable and movable reflectingelements.

Such a technical solution is described in DE 19850217 C1, inter alia,and the procedure according to that is also referred to as “Laser-Arcmethod”.

Then, it cannot be avoided that certain parts of the formed plasma arevagabonding inside of the vacuum chamber, and as a result it may come toa deposition of coating material inside of the vacuum chamber as well,and on such windows accordingly. The windows will also be provided witha coat as well. Because of that, the transparency of the windows reducesin an undesired form such that they have to be cleaned more or lessfrequently or even have to be substituted. In order to counteract thesedisadvantages window protective foils have been used which are disposedin the vacuum chamber consequently protecting the windows from acoating, however, and which will also be coated. Such window protectivefoils are available as reels, and will be uncoiled from a supply-spooland be coiled on a second spool in operation of a respective coatingplant, wherein this is performed successively or continuously inoperation of a plant. As a result, the coiling operation is carried outwith a speed of approximately two metres per hour. The supply of such afoil inside of a vacuum chamber is limited in that the water and othergases are included inside of a foil spool which can outgas, and whichundesirably influence the vacuum conditions. Accordingly, thereplacement of a spool is required after about 15 operating hours.Because of the time required for the replacement and the expenses forthe window protective foil as well, of course, the costs of fabricationincrease accordingly.

Therefore, it is an object of the invention to provide a technicalsolution by means of which undesired coating in the window area can bedistinctly reduced.

According to the invention, this object is solved with an assemblycomprising the features of claim 1. Advantageous embodiments andimprovements of the invention can be achieved with the featuresindicated in the subordinate claims.

An assembly according to the invention for the formation of coatings onsubstrates in a vacuum in which it is enabled to operate with the“Laser-Arc Method” as is known from the prior art, is improved in thatat least one permanent magnet or electromagnet is disposed between thewindow and at least one target. Then, at least one permanent magnet orelectromagnet is positioned at the side next to or above and below theoptical axis of the laser beam, respectively, and as a result a magneticfield is developed by the permanent magnet or electromagnet. Because ofthe magnetic field the laser beam can be directed in the direction tothe surface of the target.

The magnetic field developed by one or a plurality of permanent magnetsor electromagnet(s) each should have one field component which isaligned normal to the optical axis of the laser beam and/or to the planein which the laser beam will be deflected.

As already touched on in the introducing part of the description, thelaser beam can be deflected, wherein this can be preferably performedthrough an oscillating motion between inversion points in a plane.Accordingly, a window on the vacuum chamber should have an adequateshape and dimensioning by means of which it can be ensured that thelaser beam is able to scan the entire length of targets during thedeflection.

For improved protection, inside of the vacuum chamber between the windowand permanent magnet or electromagnet(s) an aperture can be disposedthrough the opening of which the laser beam is allowed to be passedthrough for the ignition of arc discharges.

In an improvement of the invention, as this is known from the prior art,a window protective foil can be disposed in front of the windowpreferably between the aperture and window, which can be uncoiled from asupply-reel and can be coiled on another reel as well in a per se knownmanner.

With the magnetic field(s) the plasma and also target material can bedeflected such that it cannot pass in the direction to the window andwindow protective foil, respectively, through which there the coating inthis area at least can be considerably reduced.

The protection from undesired coating can also be increased in that,besides the already mentioned aperture, a second aperture is disposedinside of the vacuum chamber.

Then, between the target and the first aperture and window protectivefoil, respectively, or the window a second aperture can be disposed as aseparate aperture having an opening through which the laser beam can bedirected to the target for the ignition of arc discharges. As a result,such an aperture is disposed in the immediate vicinity of targets then.

In another alternative according to the invention such an aperture canalso be provided with a corresponding assembly of at least two permanentmagnets or electromagnets which are then disposed such that they form agap which, more or less, can form an opening of an aperture. Thus, twopermanent magnets or electromagnets can be disposed such that onepermanent magnet or electromagnet is disposed on one side of the opticalaxis, and a second permanent magnet or electromagnet is disposed on anopposite side of the optical axis of the laser beam. Then, they can bealigned in parallel to each other.

With the invention the permanent magnets or electromagnets should bedisposed such that they have the same pole alignment each.

Then, there is a possibility to stagger at least two permanent magnetsor electromagnets between the window and the target such that they eachhave different distances to the target or rather to the window.

Further it is favourable that the individual elements being serviceablewith the assembly according to the invention that is the apertures andpermanent magnets or electromagnets are disposed and formed consideringthe dimensioning of targets.

With the invention, it is possible to be precise to merely use just onetarget by means of which plasma can be formed for coating of substrates.However, in another alternative a plurality of targets preferably in aline-in assembly can be provided. With a plurality of such targets thenmultilayer systems can be formed on substrates, wherein targets fromdifferent substances or mixtures of substances will be used.

Then, targets can be formed in a roller like shape or cylindrically, androtate about an axis during the formation of coatings by means of whicha uniform abrasion of target material can be further supported with theplasma formation.

As already indicated, the lengths of apertures and the width of thepermanent magnets or electromagnets used according to the invention aswell should then take into consideration the respective target length.Accordingly, the aperture openings or the widths of the permanentmagnets and electromagnets should correspond at least to the length ofone target or to the overall length of a plurality of targets disposedin an in-line arrangement such that a laser beam can be deflected overthe entire length of one target or a plurality of targets, andprotection from undesired coating can be achieved.

As already touched on, the laser beam can be oscillated in a plane andcan thus be deflected. In this case the optical axis of the laser beamis positioned in that plane in which the deflection is performed.

In the following, the invention shall be explained in more detail by wayof example.

In the drawings,

FIG. 1 is an embodiment of an assembly according to the invention in aschematic form;

FIG. 2 is a side view of an embodiment of the assembly according to theinvention; and

FIG. 3 is another embodiment of an assembly according to the invention.

In the figures it was refrained from representing a vacuum chamber and awindow formed thereon through which a laser beam 5 can be directed intothe vacuum chamber in the direction to a target 6.

FIG. 1 shows how a laser beam 5 can be directed from a laser lightsource disposed outside a vacuum chamber through a window and a windowprotective foil 4, the opening of an aperture 1 and another opening of asecond aperture 2 in the direction to a target 6. The openings of theapertures 1 and 2 are then formed in a rectangular shape and have asufficiently great length such that the laser beam 5 can be deflectedacross an overall length of one target or a plurality of targets 6.

In the embodiment shown in FIG. 1 the two permanent magnets 3 and 3′ aredisposed between the two apertures 1 and 2. As a result, the permanentmagnet 3 is disposed below the optical axis of the laser beam 5, and thepermanent magnet 3′ is disposed above the optical axis of the laser beam5. The laser beam 5 can be directed through between the two permanentmagnets 3 and 3′ in the direction to the target 6. The aperture 1 has anopening the height of which is about 10 mm, and it is disposedimmediately in front of the window protective foil 4. The opening of theaperture 2 has a height of 4 mm, and is disposed immediately in front ofthe target 6 connected as cathode then.

The two permanent magnets 3 and 3′ are disposed such that they have thesame pole alignment in the propagation direction of the laser beam 5.The field lines of the magnet fields of the two permanent magnets 3 and3′ are drawn in diagrammatically which is also applicable to FIG. 2.

The length of a target 6 which is formed in a roller like form canamount to 200 mm, or it is allowed to be longer too. Consequently,permanent magnets 3 and 3′ can be used the overall length of which atleast amounts to the target length of 200 mm. However, at the same timeit is also possible for a plurality of permanent magnets having ashorter length then to be arranged in a line wherein the permanentmagnets 3 and 3′, respectively, arranged in a line each have the samepole alignment. Thus, for example, with four permanent magnets 3 or 3′having a respective length of 70 mm and a width of 15 mm an overalllength of 280 mm can be achieved.

With FIG. 2 it is further illustrated how the laser beam 5 can bedirected via the openings of the apertures 1 and 2, and between thepermanent magnets 3 and 3′ to the surface of a cylindrical target 6.Between the target 6 connected as cathode and an anode 7 thus electricarc discharges can be ignited, and as a result a plasma 8 can be formedwhich can be used again for coating of substrates here not shown insideof a vacuum chamber.

With the invention permanent magnets 3 or 3′ having a magnetic inductionof 20 to 50 mT can be used.

In FIG. 3 another embodiment of an assembly according to the inventionis shown. Then again, a laser beam 5 for igniting electric arcdischarges is shown which is deflectable in a plane in parallel to thesurface of a cylindrical target 6 rotating about its longitudinal axis,which is directed to the target 6 through a window not shown herein, awindow protective foil 4, through openings of the two apertures 1 and 2.

Here, a permanent magnet 3 is positioned below the plane in which thelaser beam 5 will be deflected and/or the optical axis of anon-deflected laser beam 5. The field which is formed by the permanentmagnet 3 is aligned in parallel to the anode 2. On the opposite side ofthe plane or optical axis an element 9 is disposed which, as well as theanode 7, is also electrically connected to an electrical power source.With the element 9, in particular in combination with the field of thepermanent magnet, especially of 3 too, plasma 8 passing through theaperture 2, or with the modification without any aperture 2, such plasma8 reaching in this direction can be additionally deflected such thatcoating of the window foil 4 can be reduced.

Then, the element 9 can be formed as a single sheet of electricallyconducting material. It is allowed as well to be formed grid-like or,such as shown in FIG. 3, provided with strips or strip-shaped as awhole.

Then, the element 9 should be arranged and aligned as well such that thelaser beam 5 will not be impeded, however, a magnetic field developed bythe element 9 can have its effect to the plasma 8 reaching into thisarea for its desired deflection away from the window foil 4.

As a result, the element 9 can be aligned in parallel to the plane ofdeflection or to the optical axis of the laser beam 5. However, there isalso a possibility to provide an oblique inclination of the element 9with a relatively small angle of inclination starting from that side ofthe element 9 being directed to the target 6 and up to the direction ofthe aperture 1 and window foil 4.

SUMMARY

The invention relates to an assembly for the formation of coatings onsubstrates in a vacuum, wherein a plasma is formed by means of electricarc discharge at least on one target connected as cathode, and the arcdischarge will be ignited between an anode and the target by means of adeflectable focused laser beam which is directed through a window to thesurface of the target. It is an object of the invention to provide atechnical solution by means of which an undesired coating in the windowarea of a vacuum chamber can be distinctly reduced. According to theinvention, for this a permanent magnet or electromagnet is disposedbetween the window and at least one target at the side next to, above orbelow the optical axis of the laser beam, and the laser beam is guidedthrough a magnetic field developed by the permanent magnet orelectromagnet.

1. An assembly for the formation for coatings on substrates in a vacuum,wherein a plasma is formed by means of electric arc discharge at leaston one target connected as cathode, and said arc discharge is ignitedbetween an anode and said at least one target by means of a deflectablelaser beam which is directed to the surface of said at least one target,then said laser beam is directed through a window disposed on saidvacuum chamber to said at least one target, wherein between said windowand said at least one target at least one permanent magnet orelectromagnet is disposed at the side next to, above or below theoptical axis of said laser beam and said laser beam is guided through amagnetic field formed by said at least one permanent magnet orelectromagnet.
 2. The assembly according to claim 1, wherein a magneticfield developed by said at least one permanent magnet or electromagnethas a field component aligned normal to said optical axis of said laserbeam and/or to the plane in which said laser beam is deflected.
 3. Theassembly according to claim 1, wherein between said at least onepermanent magnet or electromagnet and said window a first aperture isdisposed, through the opening of which the laser beam is directed tosaid at least one target.
 4. The assembly according to claim 1, whereinsaid at least one permanent magnet or electromagnet comprises a firstpermanent magnet or electromagnet and a second permanent magnet orelectromagnet, said first permanent magnet or electromagnet beingdisposed at one side of said optical axis and said second permanentmagnet or electromagnet being disposed on an opposite side of saidoptical axis of said laser beam.
 5. The assembly according to claim 4,wherein said first and second permanent magnets or electromagnets havethe same pole alignment.
 6. The assembly according to claim 1, whereinan element connected to an electrically positive potential is arrangedon one side disposed opposite to at least said one permanent magnet orelectromagnet relative to said optical axis and/or to said plane inwhich said laser beam is deflected.
 7. The assembly according to claim1, wherein with said at least one permanent magnet or electromagnet afield is developed which is aligned in parallel to said longitudinalaxis of said anode.
 8. The assembly according to claim 6, wherein saidelement is formed plate-like, strip-shaped, grid-shaped or provided withstrips.
 9. The assembly according to claim 6, wherein said element isaligned in parallel to said optical axis of said laser beam and/or tosaid plane in which said laser beam is deflected.
 10. The assemblyaccording to claim 1, wherein said at least one permanent magnet orelectromagnet comprises a plurality of magnets or electromagnets thatare disposed in a staggered placement between said window and said atleast one target.
 11. The assembly according to claim 1, wherein twopermanent magnets or electromagnets are forming an aperture.
 12. Theassembly according to claim 1, wherein one window through which saidlaser beam is guided along across said surface of said at least onetarget has a length which corresponds to the length of said at least onetarget considering the alignment of said laser beam.
 13. The assemblyaccording to claim 1, wherein said at least one permanent magnet orelectromagnet has a width which at least corresponds to the length ofsaid at least one target.
 14. The assembly according to claim 3, whereina second aperture is disposed between said window and said at least onetarget.
 15. The assembly according to claim 14, wherein said openings ofsaid aperture(s) have a length which at least corresponds to the lengthof said at least one target considering the deflection of said laserbeam.
 16. The assembly according to claim 15, wherein said opening(s) ofsaid aperture(s) have a width or height which ensure that said laserbeam is directed to the surface across the entire length of said atleast one target.
 17. The assembly according to claim 14, wherein saidat least one permanent magnet or electromagnet is arranged between saidtwo apertures.
 18. The assembly according to claim 3, wherein betweensaid first aperture and said window a window protective foil isdisposed.
 19. The assembly according to claim 18, wherein said windowprotective foil is coilable and uncoilable by means of a mechanism. 20.The assembly according to claim 1, wherein said at least one target isformed as a roll or a cylinder, and said laser beam is directed to theouter circumferential surface of said at least one target.
 21. Theassembly according to claim 1, wherein said laser beam is deflectable ina plane by means of an oscillating motion.
 22. The assembly according toclaim 1, wherein said optical axis of said laser beam is located in theplane of the alignment.
 23. The assembly according to claim 1, wherein aplurality of said at least one target is disposed in an in-linearrangement.